| Charters Gate Residents Company Limited | Households | 2004 |
| Chawla & Sons Healthcare Ltd | Health & social care | 2024 |
| Chestnut Family Limited | Health & social care | 2021 |
| Cheylesmore (Camberley) Residents Company Limited | Households | 1985 |
| Chiltern Printers (Slough) Limited | Manufacturing | 1991 |
| Choam Services | | 2000 |
| Chris Aitken Associates Limited | Professional & scientific | 2004 |
| Christian Community Action Ministries | Wholesale & retail | 1997 |
| Christine Clarke Consultancy Limited | Financial services | 2011 |
| Church Court (Twyford) M. C. Ltd | Households | 2015 |
| Circet (NI) Limited | Construction | 2003 |
| Circet (UK) Limited | Administrative & support | 2003 |
| Citilink I.T. Limited | Information & communication | 1999 |
| Cititeam Projects Limited | Information & communication | 2001 |
| Citizens Advice Reading | Professional & scientific | 1994 |
| Clan International Transport Services Limited | Transport & logistics | 1978 |
| Classic Comic Store Limited | Administrative & support | 2008 |
| Classic Corporate Projects Limited | Professional & scientific | 1996 |
| Classic Time International Limited | Administrative & support | 2007 |
| Clayton Holdings Reading Ltd | Financial services | 2024 |
| Cleverpenny Investments Limited | Financial services | 2007 |
| Client-Server Consulting Limited | Information & communication | 1997 |
| Clifton Ingram LLP | | 2006 |
| Clinical Outsourcing Limited | Professional & scientific | 2006 |
| Clontech Projects Limited | Construction | 1996 |
| Cloud Centric Solutions Ltd | Information & communication | 2020 |
| CNJ Solutions Ltd | Agriculture & fishing | 2005 |
| Cnml Ltd | Information & communication | 2013 |
| Codelocks Direct Limited | Wholesale & retail | 2003 |
| Codelocks International Limited | Manufacturing | 1991 |
| Codelocks Limited | Extraterritorial | 2004 |
| Codernetic Ltd | Information & communication | 2013 |
| Coley Hill Court Limited | Households | 1998 |
| Colin Clayton Assistive Technology Ltd. | Information & communication | 2006 |
| College of Marketing Limited(The) | Extraterritorial | 1978 |
| Colour Compounding Limited | | 1951 |
| Comfort Lodge Reading Limited | Real estate | 1998 |
| Commertech Limited | Construction | 1988 |
| Committed Care Services Limited | Health & social care | 2006 |
| Communication, Advertising and Marketing Education Limited | Extraterritorial | 1979 |
| Comprehensive Engineers Limited | | 1971 |
| Compu-Tel UK Ltd | Wholesale & retail | 2008 |
| Computer Care (South) Limited | Information & communication | 1986 |
| Computers Online Limited | Manufacturing | 2000 |
| Concept Living Limited | Wholesale & retail | 2005 |
| Connected Digital Ltd | Information & communication | 2007 |
| Connected Place Limited | Extraterritorial | 1995 |
| Conxion Ltd | Information & communication | 2001 |
| Corporate Chauffeur Services Limited | Transport & logistics | 2006 |
| Corporate Treasury Solutions Limited | Professional & scientific | 2001 |
| Cosnetics Limited | Information & communication | 2003 |
| Country Care Southern Limited | Administrative & support | 1997 |
| Countrystore (Highway) Limited | Wholesale & retail | 2006 |
| Courtaulds Textiles (Holdings) Limited | Professional & scientific | 1983 |
| Courtney ATF Centre Limited | Manufacturing | 2016 |
| CPD Resource Limited | Professional & scientific | 2002 |
| Crackerjack Limited | Information & communication | 2003 |
| Crafty Taps Bars Limited | Wholesale & retail | 2024 |
| Craic Limited | Extraterritorial | 2002 |
| Crateline Limited | Transport & logistics | 1999 |
| CRE8ION Properties Ltd | Real estate | 2008 |
| Creative Images | | 1997 |
| Crescent Signs Limited | Professional & scientific | 2002 |
| Crighton Davies Company Limited | | 1981 |
| Cristalize Ltd | Professional & scientific | 2004 |
| Critical Mass Limited | Information & communication | 2001 |
| CRL Fire & Flood Damage Ltd | Administrative & support | 2003 |
| CRM Integrators Limited | Information & communication | 2006 |
| Crombie Enterprises Ltd | Mining & quarrying | 1999 |
| Crookes Healthcare Limited | Professional & scientific | 1941 |
| Crowthorne Chiropractic Limited | Health & social care | 2003 |
| Crowthorne Insurance Services Limited | Financial services | 2003 |
| CTI Medical Equipment Limited | Manufacturing | 1988 |
| Culturemix Arts | Education | 2003 |
| Custom Carp Boats Limited | Agriculture & fishing | 2006 |
| CWC Berkshire Ltd | Construction | 2003 |
| Cymbion Limited | Administrative & support | 1999 |
| Cyril Howes Limited | Wholesale & retail | 1950 |
| D. Alston Consultants Limited | Information & communication | 1995 |
| D.B. International Limited | Manufacturing | 1977 |
| D.E Holding UK Limited | Professional & scientific | 1981 |
| D.L. Fitt (Contracts) Limited | | 1992 |
| D.S. Redrup Limited | Transport & logistics | 2003 |
| DA Vinci Brothers Limited | Other services | 2003 |
| Damien Associates Ltd | Information & communication | 2019 |
| Daniel Property Investment Company Limited | Real estate | 1985 |
| Darren Franks Consultancy Ltd | Professional & scientific | 2023 |
| Data Obsession Ltd | Information & communication | 2003 |
| Data-Keep Limited | Professional & scientific | 1997 |
| Datasoft Computing Limited | Information & communication | 1997 |
| Datatecnix Limited | Information & communication | 1991 |
| Datavation Technologies Limited | Other services | 2026 |
| Datsomor Limited | Health & social care | 2012 |
| Davey Designs Limited | Professional & scientific | 2004 |
| David Peterson Limited | Wholesale & retail | 1997 |
| Dawn 2 Dusk Limited | Professional & scientific | 2007 |
| Dawnview Consultants Limited | Professional & scientific | 2005 |
| Dawson & Dawson Limited | Information & communication | 2000 |
| Day & Johnson Limited | Construction | 1993 |
| Decca Radio & Television Limited | Professional & scientific | 1938 |